Indium (In) has been suggested as an additive to Cu interconnects in order to improve corrosion resistance, electromigration properties, and dielectric adhesion. Being a low melting element, In readily interdiffuses with metals such as Cu, even at room temperature. In forms a protective oxide layer that imparts corrosion resistance, and serves as a good base layer to deposit the next dielectric layer in a multilayer microelectronic structure.
Indium may be selectively deposited by a chemical displacement process. However, an alternative process is to blanket deposit In on a substrate with interconnects already formed and to remove the unwanted In on the dielectric by a process involving lithographic patterning and subtractive etching. However, this is a difficult, expensive, and time consuming procedure.